How can I perform a partial symbol match on a defstruct?
In this StackOverFlow question, I created an employee database and provided a select-by-first function. How can I write a select-by-first-pattern where the record is returned if any part of the string/symbol matches?
(select-by-first-pattern 'ev); Returns all records containing "ev" (eg. Steve)
Here's the code needed to construct the database: (UPDATED: Included suggested solution)
(require 'cl) (defvar *emp-db* nil) (defun add-record (emp) (push emp *emp-db*)) (defstruct employee age first-name last-name sex children) (add-record (make-employee)) (add-record (make-employee :age 34 :last-name 'farquharson :first-name 'alice :sex 'female)) (add-record (make-employee :age 43 :last-name 'jobs :first-name 'steve :sex 'male)) (add-reco开发者_如何学Crd (make-employee :age 53 :last-name 'ballmer :first-name 'steve :sex 'male)) (defun select-by-first (first-name) (remove-if-not #'(lambda (employee) (equal (employee-first-name employee) first-name)) *emp-db*)) ;; ---------- Answer below ---------- ;; (defun select-by-first-pattern (first-name) (remove-if-not #'(lambda (employee) (if (string-match first-name (symbol-name (employee-first-name employee))) t nil)) *emp-db*)) (print (select-by-first-pattern "al")); Returns alice's record (print (select-by-first-pattern "ev")); Returns records of the two Steve's (print (select-by-first-pattern "ee")); Returns nil
If you want to do partial or pattern matches, you really should be using strings. I don't have any experience with Common Lisp proper, but Emacs has a wealth of regex-matching functions.
If you really are stuck with symbols as inputs, you could use symbol-name
(in Elisp at least) to get the name of the symbol as a string. Either way, you're going to end up comparing strings, so you might as well use them to begin with.
Use SYMBOL-NAME to convert a symbol to a string, by preserving the original case:
> (symbol-name '|Alice|)
"Alice"
For simple string searches, you can use the SEARCH function:
> (search "li" (symbol-name '|Alice|))
1
> (search "li" (symbol-name '|Dave|))
NIL
For complex pattern matching, probably this library can help.
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